1. Field
Various features relate to a vertical coupling hybrid transformer structure on semiconductor devices.
2. Background
A transformer is a device that transfers electrical energy from one circuit to another circuit through inductors, which are typically coils and/or windings. A hybrid transformer is a specific type of transformer that allows energy/power to be split in any desired proportion between two sets of receiving ports. That is, energy/power from one set of ports from a first circuit can be transferred to two different sets of receiving ports from a second circuit, or vice versa.
A hybrid transformer has several properties and may perform several functions. For example, a hybrid transformer provides bi-conjugacy between alternate set of ports, impedance matching at each port, the ability to spilt power in any desired proportion between two receiving ports, and 180 degree phase inversion of signals.
A hybrid transformer may have a balanced configuration or an unbalanced configuration. In a balanced configuration, the split of the energy/power is more evenly distributed between the two sets of ports, while in an unbalanced configuration, the split of the energy/power is biased towards one set of ports.
FIG. 1A illustrates a circuit diagram of an example of a hybrid transformer 100 found in the prior art. As shown in FIG. 1A, the hybrid transformer 100 includes a first coil 102, a first port 104 and a second port 106. The first port 104 is connected to a first capacitor and the second port 106 is connected to a second capacitor. The hybrid transformer 100 also includes a second coil 108, a third coil 110, a third port 112, a fourth port 114, and a fifth port 116. The third port 112 is connected to a replica port, the fourth port 114 is connected to a power amplifier (PA), and the fifth port is connected to an antenna.
A hybrid transformer may have insertion loss and isolation properties. FIG. 1B conceptually illustrates the various loss and isolation of a hybrid transformer in a balanced configuration. There are two types of insertion loss, a TX-ANT loss (Transmitter Antenna loss) and ANT-RX loss (Antenna Receiver loss). TX-ANT loss refers to loss from the fourth port 114 to the fifth port 116 (e.g., from PA to Antenna), The ANT-RX loss refers to the loss from the fifth port 116 to the second port 106 (e.g., from Antenna to LNA circuit). As shown in FIG. 1B, the hybrid transformer also has TX-RX isolation/leakage.
FIG. 1C conceptually illustrates the various loss and isolation of a hybrid transformer in an unbalanced configuration. As shown in FIG. 1C, the TX-ANT loss is lower in the unbalanced configuration than in the balanced configuration (as illustrated by the thicker arrow). However, the ANT-RX loss is higher in the unbalanced configuration than the balanced configuration (also illustrated by the dotted-line arrow). Different hybrid transformers will have different loss and isolation properties.
FIG. 2 illustrates a top view diagram of a lateral coupling hybrid transformer. As shown in FIG. 2, the hybrid transformer 200 includes a first set of windings 202 and a second set of windings 204. The first set of windings includes a first port 206 and a second port 208. The first set of windings 202 also includes a first set of interconnects 210. The second set of windings 204 includes a third port 212, a fourth port 214 and a fifth port 216. Also, the second set of windings 204 includes a second set of interconnects 218.
As shown in FIG. 2, the first set of windings 202 and the second set of windings 204 are located on one layer of a die. When the first set of windings 202 and the second set of windings 204 are on one layer, then lateral coupling occurs. That is, energy transfers within the same layer of the die. Major drawbacks of lateral coupling includes (i) small coupling coefficient between the first set and the second set of windings (or adjacent inductors) due to the winding spacing and metal thickness by the process limitation, and (ii) the windings take up a relatively large area. In addition, because only one layer is used, the set of windings used are asymmetrical to each other.
Therefore, there is a need for an improved hybrid transformer. Specifically, there is a need for an improved hybrid transformer that utilizes novel technology, or explores a new hybrid transformer device structure using a disruptive process technology.